Reference for checking temperature

[NeoPTLD]

I have a rod type thermometer, although I don't know how accurate it is. Are there some very precise temperature I can reproduce easily within the range of -20 and 150C?

I already tried ice water and it seems like the thermomter is off a bit. Now, I'd like to try boiling water, but I am not sure what the boiling point of water is supposed to be here.

I'm guessing I'm only a few hundred feet above the sea level. To check the thermometer, is it really necessary for me to get the most recent barometric pressure, exact elevation and calculate the theoretical boiling point of water?

 

[f95toli]

You need to know the preassure, then you can look up the boiling temperature in a table.

 

[CTho9305]

Originally posted by: f95toli
You need to know the preassure, then you can look up the boiling temperature in a table.

link

 

[RossGr]

If you need such precise measurements that you have to compensate for a few hundred feet (or even meters) of elevation then you are using the wrong insturment. The thermal mass and limited accuracy inherent in glass thermometers do not lend them selves to reading closer then about 1deg.

Call the boiling point of Water 100C

Edit:
Oh yeah, did you emerse the themometer to the thermal equivelent line in the water?

 

[NeoPTLD]

The thermometer is still off, but boiling point is slightly higher today as is the barometric pressure.

Today: 771.4mmHg corrected for sea level.
When I posted this thread: 740mmHg or so.

 

[KalTorak]

More general question: What IS a precise way to determine temperature? Does the range over which the temperature is measured matter when choosing the instrument?

 

[Fencer128]

Originally posted by: KalTorak
More general question: What IS a precise way to determine temperature? Does the range over which the temperature is measured matter when choosing the instrument?

I believe a constant volume gas thermometer is the type used to calibrate all other thermometers. I also believe it offers the most precise measure of absolute temperature available. However, it is unwieldy and impractible for just about anything other than calibration tasks.

When choosing a thermometer many things need to be considered - among them temperature range of operation - but also accuracy, repsonsiveness, whether there is physical contact with the point to be measured, etc.

Cheers,

Andy

 

[f95toli]

It depends on the temperature range.
The first thing you have to decide is if you want a primary or secondary thermometer, a primary thermometer is a device which does not need to be calibrated against another thermometer, meaning you can calculate the absolute themperature somehow if you know a for example a pressure or a voltage; gas , nuclear spin orientation, Coloumb blockade and noise thermomters are examples of primary thermometers.
Most electronic thermometers are secondary, this includes thermocouples and all semiconducting types.

If you need a really good thermometer you first have to decide on the temperature range, based on that you choose the type and then you can buy a calibrated sensor from for example www.lakehore.com (it comes with a certificate that specifies the accuracy). Today we mostly use semiconducting types (usually Si-diods).